Legal claims defining the scope of protection. Each claim is shown in both the original legal language and a plain English translation.
1. An apparatus for processing a frequency offset of a pilot signal, to stabilize spacing of sub-channels and optimize a Wavelength Division Multiplexing (WDM) communication system, the apparatus is configured in a receiver of the WDM communication system, and the apparatus comprising a digital signal processor, which is configured to: calculate at least two correlation functions of a channel by using a received signal and at least two correlation lengths, each correlation function corresponds to a correlation length; calculate at least two phases to which the at least two correlation lengths corresponds according to the at least two correlation functions, respectively, and when a difference between a neighboring first phase and a second phase in the phases to which the at least two correlation lengths correspond is greater than π, add 2π to the second phase to obtain an adjusted second phase; and perform fitting on adjusted phases to which the at least two correlation lengths correspond and calculate a corresponding slope according to a fitting result when the phase to which at least one of the at least two correlation lengths corresponds is greater than 2π, and estimate the frequency offset of the pilot signal of the channel based on the slope.
This invention relates to stabilizing sub-channel spacing and optimizing Wavelength Division Multiplexing (WDM) communication systems by processing frequency offsets in pilot signals. The apparatus is integrated into a WDM receiver and uses a digital signal processor to correct frequency deviations that can disrupt system performance. The processor calculates multiple correlation functions for a channel using a received signal and different correlation lengths, each function corresponding to a specific length. From these, it derives multiple phase values, adjusting any phase exceeding π by adding 2π to maintain continuity. If any phase exceeds 2π, the processor fits the adjusted phases and computes a slope from the fitting result. The frequency offset of the pilot signal is then estimated based on this slope, ensuring accurate sub-channel alignment and improving WDM system efficiency. The method compensates for phase discontinuities and provides precise frequency offset estimation, enhancing signal integrity in high-capacity optical networks.
3. The apparatus for processing according to claim 1 , wherein the digital signal processor is further configured to obtain the frequency offset of the pilot signal of the channel according to the phase to which the correlation length corresponds when the phase to which one of the at least two correlation lengths corresponds is less than or equal to 2π.
This invention relates to digital signal processing in communication systems, specifically for estimating frequency offset in received signals. The problem addressed is accurately determining frequency offset in a received signal, particularly when the signal includes a pilot signal used for synchronization and channel estimation. Frequency offset estimation is critical for maintaining signal integrity in wireless communications, as inaccuracies can lead to degraded performance or loss of synchronization. The apparatus includes a digital signal processor configured to process a received signal containing a pilot signal. The processor performs correlation operations on the pilot signal using at least two different correlation lengths. The correlation results are analyzed to determine the phase associated with each correlation length. If the phase corresponding to one of the correlation lengths is less than or equal to 2π, the processor uses this phase to calculate the frequency offset of the pilot signal. This approach improves accuracy by leveraging multiple correlation lengths to resolve phase ambiguities that can arise in frequency offset estimation. The method ensures reliable frequency offset detection even in challenging signal conditions, enhancing system robustness in wireless communication applications.
5. The apparatus for processing according to claim 1 , wherein the channel is a main channel or a neighboring channel, the digital signal processor is further is configured to estimate respectively a frequency offset of a pilot signal of the main channel and a frequency offset of the pilot signal of the neighboring channel; and determine channel spacing between two neighboring channels according to the frequency offset of the pilot signal of the main channel, the frequency offset of the pilot signal of the neighboring channel and a frequency of a pilot signal at a transmitting device.
This invention relates to digital signal processing in wireless communication systems, specifically for estimating and managing frequency offsets in main and neighboring channels to determine channel spacing. The apparatus includes a digital signal processor configured to process signals from both a main channel and at least one neighboring channel. The processor estimates the frequency offset of a pilot signal in the main channel and the frequency offset of a pilot signal in the neighboring channel. Using these offsets, along with the known frequency of the pilot signal at the transmitting device, the processor calculates the channel spacing between the main channel and the neighboring channel. This allows for accurate frequency synchronization and interference mitigation in multi-channel wireless systems. The apparatus ensures proper channel separation by dynamically adjusting for frequency deviations, which is critical in dense wireless environments where adjacent channels must be precisely spaced to avoid interference. The solution addresses the challenge of maintaining signal integrity and minimizing cross-channel interference in high-frequency communication systems.
6. The apparatus for processing according to claim 1 , wherein the digital signal processor is further configured to filter the received signal and acquire a filtered signal; perform frequency shifting on the filtered signal and acquire a frequency-shifted signal; and calculate the correlation function of the channel by using the frequency-shifted signal and the correlation length.
This invention relates to digital signal processing in communication systems, particularly for improving signal acquisition and channel estimation. The apparatus processes received signals to enhance performance in environments with interference or noise. The digital signal processor filters the received signal to remove unwanted components, producing a filtered signal. The filtered signal undergoes frequency shifting to align it with a desired frequency band, resulting in a frequency-shifted signal. The processor then calculates the correlation function of the communication channel using the frequency-shifted signal and a predefined correlation length. This correlation function helps estimate channel characteristics, improving signal detection and demodulation. The apparatus may also include an analog-to-digital converter to digitize the received signal before processing. The filtering step removes noise or interference, while frequency shifting compensates for carrier frequency offsets. The correlation function calculation provides insights into multipath effects and channel impulse response, aiding in accurate signal recovery. This technique is useful in wireless communication systems, radar, and other applications requiring robust signal processing.
7. A receiver comprising the apparatus for processing the frequency offset of the pilot signal as claimed in claim 1 .
A receiver system is designed to process frequency offsets in pilot signals, which are reference signals used in wireless communication systems to estimate and correct frequency errors between a transmitter and receiver. Frequency offsets can arise due to Doppler shifts, oscillator mismatches, or other factors, leading to signal degradation and reduced communication reliability. The receiver includes an apparatus specifically configured to measure and compensate for these frequency offsets in the pilot signal. This apparatus may involve signal processing techniques such as correlation, phase detection, or frequency estimation algorithms to detect the offset and apply corrective adjustments. The corrected pilot signal can then be used to improve the accuracy of channel estimation, synchronization, and data demodulation in the receiver. The system ensures robust communication by mitigating the effects of frequency mismatches, particularly in dynamic environments where frequency variations are common. The apparatus may also include filtering or tracking mechanisms to continuously monitor and adjust for frequency offsets over time. This approach enhances the receiver's ability to maintain synchronization and improve overall system performance in wireless communication networks.
8. A method for processing a frequency offset of a pilot signal, to stabilize spacing of sub-channels and optimize a Wavelength Division Multiplexing (WDM) communication system, in a receiver of a the WDM communication system, and the method comprising: calculating at least two correlation functions of a channel by using a received signal and at least two correlation lengths, each correlation function corresponds to a correlation length; calculating at least two phases to which the at least two correlation lengths corresponds according to the at least two correlation, respectively, and when a difference between a neighboring first phase and a second phase in the phases to which the at least two correlation lengths correspond is greater than π, add 2π to the second phase to obtain an adjusted second phase; and performing fitting on adjusted phases to which the at least two correlation lengths correspond and calculating a corresponding slope according to a fitting result when the phase to which at least one of the at least two correlation lengths corresponds is greater than 2π, and estimating a frequency offset of the pilot signal of the channel based on the slope.
This invention relates to stabilizing sub-channel spacing and optimizing Wavelength Division Multiplexing (WDM) communication systems by processing frequency offsets in pilot signals. In WDM systems, maintaining precise sub-channel spacing is critical for minimizing interference and ensuring reliable data transmission. However, frequency offsets in pilot signals can disrupt this spacing, degrading system performance. The method involves calculating at least two correlation functions for a channel using a received signal and at least two different correlation lengths. Each correlation function corresponds to one of the correlation lengths. From these, at least two phases are derived, each associated with a correlation length. If the difference between adjacent phases exceeds π, the second phase is adjusted by adding 2π to correct phase wrapping. If any phase exceeds 2π, the adjusted phases are fitted to a linear model, and the slope of this fit is calculated. The frequency offset of the pilot signal is then estimated based on this slope, allowing for precise correction of sub-channel spacing. This approach ensures accurate frequency offset estimation, which is essential for maintaining optimal sub-channel alignment in WDM systems, thereby improving signal integrity and system efficiency. The method leverages phase adjustment and linear fitting to handle phase ambiguities, providing a robust solution for frequency offset compensation.
9. A non-transitory computer readable storage medium for controlling the receiver of a Wavelength Division Multiplexing (WDM) communication system using the method as claimed in claim 8 .
A non-transitory computer readable storage medium stores instructions for controlling a receiver in a Wavelength Division Multiplexing (WDM) communication system. The system transmits multiple optical signals at different wavelengths over a single optical fiber, allowing high-capacity data transmission. A key challenge in WDM systems is accurately receiving and demultiplexing these signals, especially under varying channel conditions or interference. The stored instructions configure the receiver to process incoming optical signals by first converting them into electrical signals. The receiver then applies adaptive filtering to mitigate interference and noise, improving signal integrity. A synchronization mechanism aligns the received signals with the receiver's clock to ensure accurate data recovery. The system also includes error correction to handle transmission errors, enhancing reliability. Additionally, the receiver dynamically adjusts its parameters based on real-time channel conditions, optimizing performance. The medium further includes instructions for managing multiple input signals, ensuring each wavelength is correctly identified and processed. This adaptive approach allows the receiver to handle varying data rates and modulation formats, making the system versatile for different WDM configurations. The overall solution improves signal quality, reduces errors, and enhances the efficiency of WDM communication systems.
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April 14, 2020
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